"The day is over when they can stay in our country and wreak havoc. We will get them out and we are going to get them out fast!" This promise made by Donald Trump has won him both great support and disdain. In his attempts to force out the 11 million undocumented migrants in the USA, he is meeting fierce resistance. In so-called 'sanctuary cities', such as San Francisco, police are refusing to cooperate with federal immigration officials. "Our local role is not to enforce immigration laws, it is to enforce the law", Police Chief William Scott explains. However, some high-profile cases of immigrant re-offenders have prejudiced people against the approach. Don Rosenberg's son was killed in a traffic collision with an undocumented immigrant, who had been previously caught driving without a license. "He was protected by the city", he tells us, "he kept driving and he killed Drew". Despite Trump's threats to withdraw funding from sanctuary cities, San Francisco mayor Ed Lee nevertheless remains determined. "We have to fight our own federal administration in order to have the voice of America be heard."